Driven measures in a sketch

[Gwennberg]

Hi,

If I have a parameter in a sketch were I want to change side of the reference line in a other word I want to put in a negative value in the parameter to change side. I want to do this because I have used this parameter in other equations and want not delete it and replace again.

BR/ Goran

[conklinjm]

Linear dimensions cannot have negative values; however, you can get the result you want by creating work planes and projecting them into your sketch -- the first at the 'zero' point and the second offset from the first and controlled by your equation.  (Planes unlike linear dimensions are defined by their vector normal and, therefore, remember both their offset distance _and_ the direction of the offset.)

HTH

[Gwennberg]

Thanks for your answer

If I understand you right, will your solution only be usful if I planned my model with this datum planes from start?

So the only thingh is to re- measure the model and change parameter.

BR/ Goran

[harco]

If you switch the sketch dimension to driven it will unconstrain the sketch. You should then be able to drag the sketch in the required direction. When it is in the correct position remove the driven setting from the dimension. It will be positive but in the other direction. HTH

[Gwennberg]

Thanks!

So easy, I should have thought of that.

BR/Goran

[conklinjm]

  > If I understand you right, will your solution only be usful if I planned my model with this datum planes from start?

While it may help to have the datum planes from the start ... you can still add them to your part afterward and make it work; just move the EOP (End of Part) marker above your sketch and add the planes you require either from the origin system or existing geometry being sure to put in the equation for the offset, move the EOP marker below your sketch and edit it to project in the two (or more) created planes as required and constrain your existing sketch geometry to these projections.

The primary advantage of using these projected planes is that, if (and when) the value switches from positive to negative, the part model will still successfully rebuild.  While this may not be a problem in a part which can be edited, it does become one in any iFeatures that you create as most (if not all) of the sketch geometry and work features, etc. cannot be edited in the final part when the iFeature is placed therein.  A similar planar projection/offset equation technique can be used to ensure that angluar relationships are maintained within sketches as line segments unfortunately don't remember their vector direction. 

HTH

Note: The Inventor defined variables (d0, d1, d2, etc.) can be used in equations (like the plane offset) before the sketches in which they were originally created.